1. Field of the Invention
The present invention relates to a plasma processing apparatus.
2. Description of the Related Art
Conventionally, in manufacturing semiconductor devices, a plasma processing apparatus which performs various processes, for example, an etching process or a film forming process, by applying plasma onto a substrate (for example, a semiconductor wafer) disposed on a holding stage in a processing chamber is used. As the plasma processing apparatus, there is known a capacity coupled plasma processing apparatus in which a pair of opposite electrodes are configured by arranging an upper electrode on a ceiling portion or the like in the processing chamber to face the holding stage on which the substrate is held and the holding stage as a lower electrode.
In the above capacity coupled plasma processing apparatus, as radio frequency (RF) powers applied between the upper and lower electrodes, a first RF power having a relatively high frequency for generating plasma and a second RF power having a frequency lower than that of the first RF power for implanting ions are applied to the holding stage, that is, the lower electrode.
In addition, a plasma processing apparatus in which an RF power is applied to a lower electrode and a direct current (DC) voltage is applied to an upper electrode is well known in the art. In the plasma processing apparatus in which the DC voltage is applied to the upper electrode as described above, if a ground of the RF power is coated with ceramic or the like, a ground member for the DC voltage needs to be provided additionally for forming a ground (ground voltage) with respect to the DC voltage. As the ground member for the DC voltage, a conductive ring shaped member, for example, a ring shaped member formed of silicon, is provided to surround a holding stage so that the ring shaped member is exposed in a processing chamber. The ring shaped member may be configured by melting and bonding a plurality of arc-shaped members to each other (for example, refer to Patent Document 1).
As described above, in the plasma processing apparatus in which the RF power is applied to the lower electrode and the DC voltage is applied to the upper electrode, the ground member for the DC voltage, which functions as the ground with respect to the DC voltage, is provided to be exposed in the processing chamber. As a thorough examination result of the present inventor, in the plasma processing apparatus having the above structure, uniformity of process in a circumferential direction of a substrate is degraded according to an installation state of the conductive ring shaped member or the like as the ground member for the DC voltage, and thus the plasma processing may be biased. The biased processing caused according to the installation state of the conductive ring shaped member has to be corrected by opening the processing chamber to the atmosphere and adjusting the installation state of the conductive ring shaped member, and the correction takes time and effort, thereby resulting in degradation of productivity.    (Patent Document 1) Japanese Laid-open Patent Publication No. 2010-114313